code: def test_overlay_custom_saturation():
      rgb_img = np.random.uniform(size=(10, 10, 3))
      labels = np.ones((10, 10), dtype=np.int64)
      labels[5:, 5:] = 2
      labels[:3, :3] = 0
      alpha = 0.3
      saturation = 0.3
      rgb = label2rgb(
          labels,
          image=rgb_img,
          alpha=alpha,
          bg_label=0,
          saturation=saturation,
      )
  
      hsv = rgb2hsv(rgb_img)
      hsv[..., 1] *= saturation
      saturaded_img = hsv2rgb(hsv)
  
      # check that rgb part of input image is saturated, where labels=0
      assert_array_almost_equal(
          saturaded_img[:3, :3] * (1 - alpha), rgb[:3, :3]
      )
  
imports: import itertools
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_no_warnings, assert_warns
  from skimage._shared.testing import expected_warnings
  from skimage.color.colorconv import hsv2rgb, rgb2hsv
  from skimage.color.colorlabel import label2rgb
label_desc: Use image node_id 21 for calling a global function with example usage: test_overlay_custom_saturation() without return types